Nutrient/calorie tracking really only works if you measure the raw inputs or use a packaged product that gives you the info, and I imagine those are also the two cases that the AI can estimate visually.
Logging foods by image is a great way to get started being accountable with eating, and I'll use it if I'm out and don't want to manually figure out all the different components of something, but it's impossible for even the most well-trained human eye to understand food composition visually. A lot of AI-focused diet apps have gone in this direction as their primary method of input because it removes the need for a database, but the marketing these apps run that this is in anyway accurate as a primary search mechanism is, to me, really borders on abject dishonesty and sets users up for long-term failure. Just because an ingredient is invisible when prepared doesn't mean it's not there.